1. Field of the Invention
The present invention relates to a lens barrel having a linear guide mechanism provided in the lens barrel for guiding a linear moving barrel along an optical axis without the lens barrel rotating about the optical axis.
2. Description of the Related Art
A conventional lens-shutter type of zoom lens camera having a telescoping type of zoom lens barrel is widely known. In such a type of zoom lens camera, a zoom lens barrel unit is usually assembled separately from a main body (camera body) of the camera before being installed in a housing of the camera body. The housing of the camera body is usually provided on an inner peripheral surface thereof with a female helicoid and a plurality of linear guide grooves intersecting the female helicoid and extending in the optical axis direction. In the camera body having such a housing, the zoom lens barrel unit is usually installed using the following method. The zoom lens barrel unit is first inserted into the housing from a rear of the housing. Subsequently, the male helicoid, formed on an outer peripheral surface of the outermost barrel of the zoom lens barrel unit, is brought into mesh with the female helicoid which is formed on an inner periphery of the housing. Thereafter, a linear guide plate, provided with a plurality of radial follower projections, is secured to the rear end of the outermost barrel and the plurality of follower projections engage with the plurality of linear guide grooves of the housing.
According to such an installing method, it is necessary to carry out several processes to install the zoom lens barrel unit in the housing of the camera body. This complicated installation process is troublesome and increases installation time.
When a lens barrel is designed having a guide groove or a cam groove formed on an inner peripheral surface which engages with a follower projection provided on a predetermined member to guide the same along the groove, the width and depth of the groove are determined before the whole dimension of the lens barrel (thickness, diameter, etc.) is determined. Also, the width and depth of the groove need to be sufficient to maintain the mechanical strength of the lens barrel. Therefore, in general, such a lens barrel having a guide or cam groove tends to be designed as a member which is too thick and too large.